Tungsten inert gas welding, arc gas welding, electron beam welding, and the like, are widely employed in the joining of fluid supply system pipes having welded portions, gas parts, or wetted parts. In such conventional welding technologies, no consideration was given to the burning of the weld surface, the surface roughness of the welded portion, or the deposition of metal fumes generated from the fused portion, and it was determined that corrosion and metal contamination occurred with respect to extremely active special material gasses. Furthermore, with respect to inert common gasses, as well, though actual problems do not occur over short periods of time, it is thought that there are likely to be reliability problems over a longer period of time.
Using FIG. 7 below, the deposition of metal fumes, the surface roughness of the welded portion, and the deposition of chrome carbides on the surface in accordance with the conventional method of installation for fluid supply pipe systems will be explained in greater detail. FIG. 7 shows a welded portion of pipe materials welded by means of tungsten inert gas welding. In the Figure, reference 701 indicates a tungsten electrode, and reference 702 indicates pipe materials which are subjected to welding. Reference 703 indicates a welded portion, while reference 704 indicates metal fumes which are generated at the fused portion thereof. These metal fumes 704 are deposited on to the surface of the pipe material 702 at the downstream side of the welded portion 703 as a result of the arc gas or back-seal gas flow, and become deposited metals 705. These deposited metals 705 do not pose the problem of separation with respect to inert gasses; however, under the flow of a corrosive gas, for example, hydrogen chloride gas, the deposited metals 705 adhering to the surface separate, and contaminate the gas atmosphere. The metals which separate have been detected to be Fe, Ni, Cr, and Mn, which are chiefly contained in the metal materials. These impurities have a great adverse effect on LSI characteristics, so that they pose a serious problem in semiconductor manufacture.
The present invention was created in light of the above circumstances; it has as an object thereof to provide a super high purity fluid supply system, and an installation method therefor, which is capable, during installation of a super high purity gas supply system, of removing metals deposited in the vicinity of the surface of the welded portion and on interior portions of the fluid supply system, and preventing in advance the contamination of, for example, a semiconductor manufacturing apparatus or the like, into which a gas, pure water, or chemicals are introduced through this fluid supply system.